It is common practice to employ a drilling derrick when drilling wells into the earth during the search and extraction of oil and gas. Such drilling derricks or rigs may be anywhere from twenty feet tall to over one hundred feet in height.
Conventionally, in such a drilling operation, the derrick will employ what is called a crown block which is rotationally engaged at the top of the derrick. The crown block employs one or more sheaves over which a cable is threaded. The crown block and cable support a traveling block which is suspended by the cable below the crown block. A first end of the cable extending from the crown block is connected to a drum which rotates under power inside of a drawworks. The drum is generally engaged to a source of power such as an engine or motor using a clutch when in a powered state and to a brake to prevent rotation when the drum is not in a powered state. The other end of the cable is called a deadline and is connected through a deadline anchor to a storage reel which allows the inclusion of more cable to the system.
During operation of the derrick, the drum when powered operates to reel and unreel the cable around the crown block thereby translating the traveling block, and any load engaged thereto, upward toward the crown block and back toward the ground depending on the rotation direction of the drum. When engaged to the drilling pipe, the segment length of the pipe will generally determine the length of travel of the traveling block toward the crown block. Exceeding this travel slightly is only an occurrence allowed when a longer length segment is engaged, or a segment with a collar or the like. It is important that the traveling block not contact the top of the derrick or the crown block during operation of the equipment or serious damage to the equipment can result. Injuries to workers below are a constant threat from such an impact. Consequently, an automatic shutoff with an override to allow for slightly longer segments is preferable.
Further, the weight or load of the mass of the pipe in the bore, can be extreme and easily cause an over-pull on the cable and rig. Over-speed movement of the mass and the resulting force from the mass acceleration, can also cause an over-pull and seriously damage the equipment by exceeding the strength of the components and breaking them. Additionally, the weight alone of the assembled pipe segments can be cause for concern if it is approaching system over-pull limits.
Still further, contact by the crown block and traveling block, sufficient to damage the equipment and cabling, will concurrently cause a loss of engagement to the load being hoisted, allowing it to fall. Such falling pipe, cable, traveling block, and equipment components will generally cause serious injuries or untimely death to workers below if allowed to occur.
It is consequently extremely important that the worker operating the drawworks continually exercise extreme care in how far the traveling block is allowed to translate toward the crown block. Most workers in this highly competitive environment work long tiring hours which can eventually cause loss in their concentration ability while at their post. A momentary lapse in judgement or attention with regard to the rig however, can have life threatening consequences. Further, it can be especially hard to judge the distance of the traveling block from contact with the crown block in cases where the derrick is very tall, at night, and in poor lighting conditions such as at sunset or sunrise.
Additionally, it is also important that the force of the mass of the load being hoisted be constantly monitored in this environment since workers are unable to mentally calculate such loads. Excess speed, or excess weight even at normal speeds, can easily develop a force on the equipment exceeding cable and equipment limits which as noted can also cause collapse of the system or suspended equipment upon workers and damaged drilling rigs.
U.S. Pat. No. 3,677,520 (Koomey) teaches a device for preventing the traveling block of a drilling rig from being drawn into the top of the rig by the employment of a toggle valve engaging the cable on the cable drum to control the rig brake and rig clutch. A manual safety override is provided to allow for longer lengths of drill pipe or drill collars or other special tools to be handled instead of a set length of pipe. Koomey, however, is a mechanically operated system engaged to the drawworks and requires that the cable hit a trip switch which cuts off air communicated to the drum clutch and vents it to the brake. It is thus susceptible to mechanical failure.
U.S. Pat. No. 4,284,253 (Uribe) improves on the system of Koomey. In combination with the mechanically operated system similar to Koomey, Uribe provides an emergency cutoff switch allowing anyone to manually initiate the clutch release and braking of the drum during operation.
Consequently, there is an unmet need for a system that is easily interfaced with the rig operating components and monitors a plurality of hazards to equipment and workers automatically. So interfaced and operatively engaged, such a system should initiate an automatic cessation of operation prior to rig damage and exposing workers to potential injury. Such a system should concurrently monitor traveling block height as well as the load on the system from the assembled pipe segments and other components contributing to the mass being hoisted or lowered. Such a device, in addition to providing a worker-activated emergency cut off, should interface with rig airlines and electrical components to automatically stop the hoist system if the force of the load being hoisted exceeds a predetermined system maximum load.
With respect to the above, before explaining at least one preferred embodiment of the invention in detail, it is to be understood that the invention is not limited in its application to the details of construction and to the arrangement of the components or steps set forth in the following description or illustrated in the drawings. The various apparatus and methods of the invention are capable of other embodiments and of being practiced and carried out in various ways which will be obvious to those skilled in the art once they review this disclosure. Also, it is to be understood that the phraseology and terminology employed herein are for the purpose of description and should not be regarded as limiting.
As such, those skilled in the art will appreciate that the conception upon which this disclosure is based may readily be utilized as a basis for designing other automatically operated multiple component monitoring systems for drilling rigs and the like, for carrying out the several purposes of the present disclosed device. It is important, therefore, that the objects and claims be regarded as including such equivalent construction and methodology insofar as they do not depart from the spirit and scope of the present invention.